The present application relates to semiconductor fabrication, and more particularly to the fabrication of semiconductor dies with electromagnetic radiation blocking components.
New classes of low-profile miniaturized microsystems are being developed for a myriad of new applications; some of which require semiconductor dies having dimensions on the order of 100 μm or less. While the technologies for creating such small and thin semiconductor dies are well-established, techniques required to make these semiconductor dies immune to electromagnetic radiation such as ultraviolet (UV), visible and infrared (IR) light, without the need for additional packaging, are still lacking. Considering an application with two types of semiconductor dies in which the semiconductor die of the first type contains a light sensor on a portion of its surface, and the semiconductor die of the second type contains charge pumps to drive an analog output voltage signal to an actuator, it has been found that the bare die of the first type experiences an unwanted shift in oscillator frequency when it is illuminated, while the bare die of the second type experiences a dramatic drop in output voltage signal. These effects are both caused by generation of minority carriers in the exposed semiconductor body of the dies. Adding an electromagnetic radiation blocking layer to the top circuit side only protects the semiconductor dies from topside illumination, but scattered light can still reach the sides and backsides of the semiconductor dies, creating the same spurious effects. Adding an opaque electromagnetic radiation blocking layer surrounding the semiconductor dies at die level is not practical, especially for profile-sensitive applications since there is no room to add any external package at all. Furthermore, for very small semiconductor dies, it is very inconvenient, and in certain cases is highly unprofitable, to add an opaque electromagnetic radiation blocking layer at the die level. Therefore, there remains a need for a method that allows for fully encapsulating semiconductor dies with electromagnetic radiation blocking components at the wafer level.